Multiprocessing: Functions and Features

von Christian Vilsbeck

SMP Operating Systems

In order to take advantage of multiprocessor hardware, the operating system needs to support SMP accordingly. The same applies to applications. Software, which is programmed single threaded, does not run faster in a multiprocessor environment. Systems, which run multiple CPU intensive programs simultaneously, are an exception. If a computer runs a web server, a database, remote access and processes at the same time a number of print and file jobs, also single threaded applications will profit from the use of multiple CPUs. The reason: A MP-capable operating system distributes different applications to different CPUs. If CPU statistics reveal that multiple programs cause a significant load on the processor, a MP-system makes sense in any case. It is important to know, that for almost every operating system there are different versions of SMPs and Kernels which relate to a certain number of processors. For example, Windows 2000 supports only up to 2 CPUs. The server versions are able to support up to 32 processors (Windows 2000 Server Datacenter), depending on the hardware. QNX and BeOS handle up to eight processors. The following table lists some x86-comaptible operating systems